Understand Contaminated Sites

On this page:

• What are environmental health risks?
• What is a stressor?
• What is an exposure pathway?
• How Does EPA Address Risks from Superfund Sites?
• What Does "Acceptable" Levels of Contamination Mean? Isn’t Any Amount Dangerous?
• What are cumulative impacts? 

What are environmental health risks?

EPA considers environmental health risks to be the chances of harmful effects to human health and/or to ecological systems resulting from exposure to an environmental stressor. 

What is a stressor?

Stressors are defined as any physical, chemical, social, or biological entity that can induce a change (either positive, negative, or neutral) in health, well-being, and quality of life (either now or into the future). Hot temperatures, air pollution, inadequate nutrition, and viruses are all examples of stressors.

What is an exposure pathway?

An exposure pathway is the link between a contaminant source or stressor and a receptor.  For example, chemicals found in yard soil can be ingested residents who might inadvertently swallow some dust or touch their mouth with dirt on their fingers. Other exposure pathways include dermal (skin) and inhalation.  

How Does EPA Address Risks from Superfund Sites?

Superfund risk assessments determine how threatening a contaminated site is to human health and the environment. Risk Assessors seek to determine a protective or acceptable level  for each contaminant of concern present.

For humans, this is a level at which it is unlikely that the contamination will cause health concerns and the probability of cancer is very small. 

For ecological receptors, determining the level of risk is more complicated as we must consider the impact on a variety of plants, animals, and ecosystems. 

Every Superfund site gets its own risk assessment to address the contamination unique to that site. The risk assessment also identifies the range of potential health effects that may be caused by the contamination. 

It's important to note that risk assessments are estimates. Risk assessments answer the question: If we did nothing to clean up this Superfund site, what would the current and possible future risks be? By answering this question, we can select the best cleanup strategies to manage the risks to an acceptable level.

What Does "Acceptable" Levels of Contamination Mean? Isn’t Any Amount Dangerous?

Acceptable levels are levels at which it is unlikely that the contamination will cause health concerns and the probability of cancer is very small. We can determine this level through our risk assessment process.  The presence of contaminated waste in your community is understandably concerning. The reality is that, at many cleanup sites, it’s not possible to remove all of the contamination. That means we have to determine a level that is low enough is low enough to be protective of human health. We can do this through our risk assessment process.

What are cumulative impacts? 

In everyday life, people are exposed to numerous pollutants from a wide array of sources through multiple media and pathways. Cumulative impacts comprise of stressors from multiple pathways. Chemical stressors in environmental media (air, water, land) and non-chemical stressors (e.g., social determinants of health, extreme weather events) that aggregate over time from one or more sources in the built, natural, and social environments, are referred to as cumulative impacts. In communities, particularly those already overburdened, disproportionate impacts can arise from unequal environmental conditions. 

EPA supports federal, Tribal, state, and community decision-making by strengthening the scientific foundation for assessing cumulative impacts, exposures, and risks through existing and new methods, tools, data, and monitoring.